1. Field of the Invention
The invention relates to a perpendicular magnetic write head including a magnetic shield layer provided on a magnetic pole through a nonmagnetic gap layer, and a method of manufacturing the same.
2. Description of the Related Art
In recent years, an improvement in performance of a magnetic write head has been demanded, due to an increase in an areal recording density of a magnetic recording medium (hereinafter, referred to as a “recording medium”) typified by a hard disk. To address this, a perpendicular magnetic write head, in which a direction of a signal magnetic field is set in a direction intersecting a surface of the recording medium, has been developed. The reason is that there are such advantages that a linear recording density increases, and a recording medium on which recording has been already performed is less susceptible to thermal fluctuation.
A perpendicular magnetic write head is provided with a main magnetic-pole layer for leading a magnetic flux generated in a thin-film coil to a recording medium. The main magnetic-pole layer includes a tip portion (a magnetic pole) having a fine width, which releases the magnetic flux to generate a magnetic field for recording (a perpendicular magnetic field). The perpendicular magnetic write head is arranged with a magnetic shield layer for recording, which is provided on the magnetic pole through a nonmagnetic gap layer, in order to increase a magnetic field gradient in a track-width direction (a cross-track direction) and in a direction intersecting thereto (a down-track direction).
More specifically, a metal-coating foundation layer is formed in three directions of a main magnetic-pole portion through a gap layer, and a shield layer is so formed as to surround the main magnetic-pole portion from the three directions by using the metal-coating foundation layer (for example, see Japanese Unexamined Patent Application Publication No. 2004-348928). The three directions here refer to both sides in the cross-track direction and to a trailing side in the down-track direction. Also, a pair of metal-coating foundation film are so formed as to sandwich the main-magnetic pole from above and below, in which one of the metal-coating foundation films is used to form a trailing shield, and a pair of side shields are so formed as to sandwich the main-magnetic pole from both sides through a nonmagnetic insulating film (for example, see Japanese Unexamined Patent Application Publication No. 2007-257711). In this case, a nonmagnetic material such as gold (Au), ruthenium (Ru), rhodium (Ru), or platinum (Pt) is used as a formation material of the metal-coating foundation film. Incidentally, a magnetic material such as a nickel-iron-cobalt alloy (NiFeCo), a cobalt-iron alloy (CoFe), or a nickel-iron alloy (NiFe) may also be used as the metal-coating foundation film (for example, see Japanese Unexamined Patent Application Publication No. 2007-250074).
In these days, the areal recording density of the recording medium is increasing more and more, and thus a perpendicular magnetic write head, which can address the increase in the areal recording density, has been desired to appear. However, in the perpendicular magnetic write head in which a recording process is performed substantially in a trailing edge of a magnetic pole, an increase in a magnetic field gradient and a suppression of generation of a side erase are in a trade-off relationship. Thus, it is difficult to satisfy both of them at the same time, since the side erase tends to occur easily in the cross-track direction when a magnetic field intensity is increased to increase the magnetic field gradient in the down-track direction, whereas the magnetic field gradient decreases in the down-track direction when the magnetic field intensity is decreased to suppress the generation of the side erase.
For these reasons, it has been strongly desired to increase the magnetic field gradient of the perpendicular magnetic field, while suppressing the generation of the side erase.